Pressure sensitive adhesives have wide spread use as a bonding agent for paper and textile substrates in the preparation of tapes, labels, decals and the like. For self-wound tapes the substrates are coated on one side with a pressure sensitive adhesive and a release agent on the other side. The release coating serves to permit the tape to be wound onto itself and then permit the release of the tape without removing the adhesive, destroying the textile or paper-based substrate, or decreasing the performance of the adhesive.
The ability of the release coating to effect release of the pressure sensitive adhesive from the back side of the substrate is only one of the requirements for a commercially acceptable release agent. One of the requirements of a release coating is that none of its components migrate into the pressure sensitive adhesive during storage of the tape or adhere to the adhesive surface during the unwinding of the tape. Migration or adherence of the release agent into the pressure sensitive adhesive tends to diminish the tackiness of the adhesive and tends to render the tape, film, etc. unusable. Another requirement of a release coating is that it be able to withstand long storage times and variations in temperature and humidity. Deterioration of the release agent over time may cause the pressure sensitive adhesive to adhere to the release coat often resulting in a tearing of the substrate during the unwinding of the tape.
Representative patents which describe a variety of release coatings for pressure sensitive adhesives are as follows:
U.S. Pat. No. 4,386,183 discloses a release coating based on polyvinyl alcohol. A variety of release materials for pressure sensitive adhesives are disclosed and these include silicones, fluorocarbons, fatty acid/metal complexes and hydrocarbon waxes. The release coating composition comprises polyvinyl alcohol, and a migratible release promoting agent, a water soluble salt of a coordinating metal and a water soluble boron compound.
U.S. Pat. No. 5,284,690 discloses aqueous release coatings for pressure sensitive adhesives based upon a water soluble polymer and an aqueous dispersion of an organic compound having at least one fatty acid ester and one quaternary amine. The polymeric component of the release component is based upon an acrylic ester monomers such as methyl or butylacrylate, styrene, vinyl acetate and the like. Acid functionality is incorporated into the polymer through polymerization of unsaturated acids such as acrylic or methacrylic acid. Examples of organic compounds having at least one fatty acid ester and a quaternary amine include di and triglycerides having a quaternary amine functional group replacing one of the fatty acid groups include lecithin and hydroxylated lecithin.